Hi, welcome to the Board. There's a thread down the page here, from Jan. 21 about CBBs and feeding etc. (
http://www.canreef.com/phpBB2/viewtopic.php?t=3652)
Some good info in there, also check out wetwebmedia.com - they have a "Chelmon FAQ" that is extensive.
I agree with dba, the FW mysis is the real deal, and seems to be the favourite food after aptasia. Someone else said theirs eats the mysis like popcorn - that's about it!
It may take a few days to clue in to it, but when the thawed pieces float down over the rocks or across the bottm, it tends to be irrestible, IME.
Also, although my tank is not big, it's more or less a dedicated CBB tank, with a couple of other small, docile roomies. Being a skittish thing to begin with, I wanted to offer a calm environment for it. Seemed to help in this case.